Although unguided or minimally guided instructional approaches are very popular and intuitively appealing...these approaches ignore both the structures that constitute human cognitive architecture and evidence from empirical studies over the past half-century that consistently indicate that minimally guided instruction is less effective and less efficient than...approaches that place a strong emphasis on guidance of the student learning process. The advantage of guidance begins to recede only when learners have sufficiently high prior knowledge to provide "internal" guidance.
A few selections from the main body:
Minimally guided instruction appears to proceed with no reference to the characteristics of working memory, long-term memory, or the intricate relations between them. The result is a series of recommendations that most educators find almost impossible to implement...because they require learners to engage in cognitive activities that are highly unlikely to result in effective learning. As a consequence, the most efefctive teachers may either ignore the recommendations or, at best, pay lip service to them. (pg. 76)
Inquiry-based instruction requires the learner to search a problem space for problem-relevant information. All problem-based searching makes heavy demands on working memory. Furthermore, that working memory load does not contribute to the accumulation of knowledge in long-term memory because while working memory is being used to search for problem solutions, it is not available and cannot be used to learn... The consequences of requiring novice learners to search for problem solutions using a limited working memory or the mechanisms by which unguided or minimally guided instruction might facilitate change in long-term memory appear to be routinely ignored. The result is a set of differently named but similar instructional approaches requiring minimal guidance that are disconnected from much that we know of human cognition. (pg. 77)
None of [this] would be important if there was a clear body of research...indicating that unguided or minimally guided instruction was more effective than guided instruction. In act...the reverse is true. Controlled experiments almost uniformly indicate that when dealing with novel information, learners should be explicitly shown what to do and how to do it. (pg. 79)
After a half-century of advocacy associated with instruction using minimal guidance, it appears that there is no body of research supporting the technique. In so far as there is any evidence from controlled studies, it almost uniformly supports direct, strong instructional guidance rather than constructivist-based minimal guidance during the instruction of novice to intermediate learners. Even for students with considerable prior knowledge, strong guidance while learning is most often found to be equally effective as unguided approaches. Not only is unguided instruction normally less effective; there is also evidence that it may have negative results when students acquire misconceptions or incomplete or disorganized knowledge. (pg. 83)
There are well over a hundred references into the literature. I'm going to have to think hard about how I've been teaching, and how I should teach. I'm also going to keep an ear open when my daughter starts junior kindergarten to see whether her teachers are basing their methods on evidence or wishful thinking.